6 12 months months Average of gains of test group in excess of control -1.035 -3.14 Median of gains of test group in excess of control -1 -3 P. E. of difference +-1.10 +-1.84 Average in terms of P. E. - .94 -1.71 Median in terms of P. E. - .99 -1.63 The result after twelve months remains the same as that after the six months' interval. A gain or loss of two or three points in I.Q. is negligible, so that the mean gain of the test group in excess of the control is practically zero at the end of each period. Variability increases with the length of the interval. One case in the test group (case 4) gained nothing in six months, but showed a gain of 15 points after 13 months. However, there is a control case to match this,--case 15, who gained 1 point in the first six months and 20 points after 10 months. Case 20 in the test group lost 4 points in the first six months, but gained back these and 10 additional in the second period. But control No. 1 gained 5 points in the second interval after having lost 4 in the first. On the other hand several cases lost in the second period, as compared with the first. Test group case 7, for example, gained 8 points in the first six months, and lost 6 of them in the second. Case 3 in the same group lost 3 points in the first period, and failed to regain any of them. Case 12 lost 3 points in six months and 9 more before the end of 12 months. In the control group, case 23 gained 15 pounds in the first six months and lost eight of them in the second. Summing up gains and losses in the second period, for both groups: TABLE XXI I.Q., Second Retests, 21 Pairs N[16] Test Group (A) Control Group (B) Test 1 Test 3 Gain Test 1 Test 3 Gain A-B